In radiology departments, “x-rays” or similar medical images are often taken of a region of a patient's body, where the body part of interest is positioned between a source of x-radiation and an x-ray image detector. A latent image of the desired region is first captured on an x-ray detector, traditionally film having an emulsion of silver halide which is sensitive to x-radiation. The film is contained within a rigid, protective, light tight cassette which is openable to remove film for processing once exposed to radiation.
Chemical processing of film is required. Film is manually removed from cassettes in darkrooms and introduced into processors which chemically develop films to produce the desired diagnostic images. A new film is place into cassette, in preparation for subsequent exposure.
“Daylight” processors were developed eliminating the need for darkrooms. The daylight processors automatically remove film from a cassette inserted therein and chemically process and replace new film in the cassette. The cassette is then ejected from the processor for removal and subsequent reuse. The next cassette to be processed would then be inserted into the daylight processor.
Digital Radiography emerged in the latter 20th Century. There are two branches of Digital Radiography. Computed Digital Radiography (CR) and Direct Readout (DR) Digital Radiography.
Computed Radiography (CR) is rapidly replacing conventional silver halide film based x-ray. CR utilizes a reusable medium (e.g., a photostimulable phosphor (PSP) embedded in an imaging plate (IP)). The IP is housed in a protective cassette and of the same size as the cassettes used with film. Once introduced into automatic PSP readers, the cassettes are opened or uncovered sufficiently to access the imaging plates for processing. The imaging plates are laser scanned and made available for viewing, printing and archiving through modern computer imaging technologies. The imaging plates are erased and replaced in the protective cassettes and ejected automatically, thus being made ready for reuse.
By replacing film technology, CR eliminates the need for chemicals, waste product recovery and recycling, film transport, and archiving expenses encountered with film.
The digital images can be enhanced with features similar to conventional image-processing software, where image parameters such as contrast, brightness, filtration, and zoom may be manipulated. In addition, since CR uses the same cassette sizes used with film, it is compatible with existing x-ray exam room equipment, thus making transition to digital technology less costly.
Most recently, Direct Readout (DR) digital radiography has emerged to capture a growing share of the diagnostic imaging market. In DR, detector arrays are utilized to capture a desired latent radiological image. The detector arrays are built into x-ray exam room equipment and “hard wired” to electronic devices. By using several different technologies, the desired images are extracted and digitized.
To its advantage, DR eliminates the need for film, imaging plates and cassettes. However, since DR does not use cassettes it generally can not be used with existing x-ray room equipment. The major disadvantage of DR is the high initial cost of the equipment required to implement the system. Since DR does not use cassettes, no further discussion of DR will be included hereinafter.
When introduced, computed radiography (CR) processors presented as single cassette storage phosphor readers or “single loaders”. These devices, still being successfully marketed, require an operator to manually load an exposed cassette into an insertion slot/opening in the device. After the phosphor plate is removed from the cassette by the processor, the latent image is scanned and digitized and the phosphor plate is prepared for reuse (erased) by of exposure to intense light and is then returned to the cassette. Erased cassettes (called “clean” in the trade) are manually removed from the same insertion slot or a separate ejection slot and placed with other “clean” cassettes at a nearby or adjacent computer workstation to be used for preparing cassettes for the next patient exam.
Newer PSP readers eventually were developed. These “multicassette” storage phosphor readers or “multiloaders” incorporate input locations or buffers for receiving exposed cassettes and automate the insertion of cassettes/imaging plates into the readers for processing. Each cassette is ejected automatically to a separate output buffer after processing and erasure render it once again “clean”.
When preparing “clean” cassettes for the next exam, each cassette required for the upcoming study can be digitally tagged at a nearby or adjacent workstation with patient and exam information. This embodiment enables more than one examination to be performed concurrently. In both “single” and “multi” loader environments, more than one exam room and x-ray technologist use a centrally located processor. Each processed image, regardless of patient is digitally routed to the correct patient's “digital” file.
With limited workspace in many situations, a problem arises when “clean” cassettes being prepared for the next exam by a user are co-mingled with exposed cassettes awaiting manual insertion into the “single” loaders. The potential of double exposing a cassette already containing a latent image is possible, leading inevitably to repeat exams, additional patient exposure to the effects of ionizing radiation and general disruption of orderly workflow.
Other well-known problems arise when media cassettes are temporarily queued awaiting processing in “single loading” devices.
There is generally great pressure on radiologic technologists or other personnel to return processed images as quickly as possible. A first in, first out (FIFO) queue philosophy is generally established for the processing. The media cassettes may be of different sizes. If they are merely stacked one upon another, it is difficult to maintain processing in a FIFO queue. To do so, the bottom cassette must be withdrawn from the stack of media cassettes, often requiring two hands, one to lift the upper cassettes, while withdrawing bottom cassette with the other hand.
If the bottom media cassette is a small cassette and overlaying cassettes are larger, it is simply easier to remove and process the top cassette on the stack. Even if the bottom cassette may readily be removed, human nature being as it is, it is virtually inevitable that out of sequence cassette processing will, at least occasionally, occur.
Also, using the make shift arrangements typically found in radiology departments, it is not uncommon for cassettes to be dropped and damaged, thereby not only disturbing the processing order but potentially damaging the expensive cassettes.